This invention relates to magnetic recording media, and more particularly to a magnetic recording medium which is employed in the technical field of magnetic printing or magnetography in which a magnetic latent image is formed and then visualized (e.g., developed).
Heretofore, two methods have been employed in forming a magnetic latent image.
In one of these methods, AC current modulated with an image signal is applied to a magnetic head which is in close contact with a belt-shaped magnetic recording medium, so that a magnetic latent image is formed according to the AC current. In the other method, DC current modulated with an image signal is applied to a heat generating element which is in close contact with a magnetic recording medium having a relatively low magnetic transformation point, so that a magnetic latent image is formed according to the DC current. In this case, an AC magnetic field is applied to the magnetic recording medium which is heated to higher than the magnetic transformation point.
In the first method described above, it is essential to drive a number of magnetic heads which are juxtaposed over the recording medium, in order to increase the recording speed. However, since the manufacture of such a magnetic head array requires a highly developed technology, the manufacturing cost is accordingly high. Thus, the first method is not practical.
On the other hand, a heat generating element array having a number of heat generating elements juxtaposed for use in the second method can be manufactured relatively readily. One example of the formation of a magnetic latent image according to the second method will be described with reference to FIG. 1.
A magnetic recording medium 1 having a relatively low magnetic transformation point is supported by a base layer 2 and is in the form of a belt. A heat generating element array 3 has a heat generating part 4 which operates while being in close contact with the recording medium. A current signal is applied to the array 3 according to image data in order to heat the magnetic recording medium 1 to a temperature higher than the magnetic transformation point. In this operation, AC current flows in a winding 6 on a magnetic core 5, and an AC magnetic field is created in the gap of the core. When the magnetic recording medium 1 is cooled, thermal residual magnetization is caused, so that the AC magnetic field remains as a magnetization pattern in the medium 1. The magnetic recording medium in this method is made of CrO.sub.2 for instance. However, in general, it is difficult to obtain chromium compounds because of evironmental reasons. Furthermore, since the recording medium is prepared by coating, it is impossible to contain more than 30 to 40% CrO.sub.2 magnetic particles having a magnetization characteristic in the recording medium, and therefore the use of CrO.sub.2 is not suitable for the case where a high magnetization characteristic is required, or where recording must be carried out with high density.